Ravens are complex birds. Not only are they able to imagine being spied upon, it's now been found that they are able to make plans for the near future.

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Cognitive scientists from Lund University, Sweden, spent hours watching the corvids to determine that they are able to think ahead to future scenarios. It's a behaviour that's previously only ever seen in humans and great apes. The research also showed ravens were willing to miss out on a reward now to get a better one in the future.

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"We show that ravens plan for events with delays of up to 17 hours, exert self-control and consider temporal distance to future events," the scientists wrote. "Their performance parallels that seen in apes and suggests that planning evolved independently in corvids, which opens new avenues for the study of cognitive evolution."

The small experiment involved four captive, hand-raised adult ravens – two males and two females. A fifth bird was meant to be involved in the study but it was deemed too neophobic – or scared of new things – to take part.

During the tests the birds were shown a box that had a tube sticking out the top. There were three stones in the testing space as well as wooden chips on the floor. The birds were taught that if they dropped a stone into the tube, they would be given a treat. If they tried to drop anything else down the tube, no food would be released.

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Over the course of the experiment, the box was taken away and they were moved to another testing ground where a new box and items were introduced. In the majority of cases the birds had learnt to pick the stone to receive the snack (a dog biscuit). They were able to complete the task better than four-year-old children.

In a separate situation, the ravens were taught that a token (in the form of a bottle top) would get them a greater reward than other items they were given. This led to them learning and being able to replicate the actions up to 17 hours later.

A third experiment tested "planning in a self-control context". The birds were given the choice of a dog biscuit right now or the option to select a stone or bottle top and receive a greater reward later: in most cases the birds decided to wait.

Overall, the researchers say ravens are able to make decisions for their futures "outside their current sensory contexts". Based on similar studies they're better at it than many apes and when bartering, ravens are better than orangutans, bonobos and chimpanzees.

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The work is the latest study that proves how advanced raven intelligence is. In April 2016, a study revealed ravens have the same level of self-control as chimpanzees despite having smaller brains. The work, also from Lund University, showed the birds were able to get a treat from inside a transparent cylindrical tube using holes at the end, instead of pecking at the plastic.

It's also been shown that ravens get paranoid when they believe they're being spied upon. A study found that if a nearby peephole was open, ravens guarded pockets of food against discovery in response to the sound of other birds – even if they didn't see another bird.